When do you stop making mods?

The problem with mods is that depending on how they're executed some are difficult to totally impractical to remove later when you sell the unit. I'm as guilty as anyone, having modded the life out of every camper we've ever owned, some ultimately not so good, others that proved in time to be invaluable, BUT if there's ever another "next" camper for us I'll keep the mods to a minimum and those that I do go ahead with will when possible be designed so as to be easily removable later. Case in point - I've always installed a powered potable water transfer system on any trailer we've owned, next time it'll be portable with the pump mounted in a case of some sort, totally separate from the trailer itself. Same with any inverter I might want to use - portable. At least my hard wire EMS I was smart enough to install so it can be instantly removed at any time. :B

I keep up with the maintenance each spring. As far as mods... I just modify what is needed for our comfort and safety, we don't have to have a lot of gadgets, etc...

I keep my RV'S so long I have to update technology every so often. I heavily modified when I purchased it new so maintenance is about all I need.

Modifications or maintenance? Maintenance is ongoing, mods are not.

That is a good question, I guess for as long as it makes sense verses selling / upgrading to a new RV. I have been asking myself this same question, though in my case it is a 16 year old class A with about 85,000 miles on the odometer.

When I'm dead!
Seriously, while I don't need to do much to my truck (just little cosmetic stuff), the mods to the trailer will go on as long as I own it. At least it did with my last TT, which I had for 13 years.
I spend last winter fixing all the manufacturing mistakes and sloppiness in our new TT.
This winter I plan on removing the fridge and fixing its installation so it works as well as it can.